7... d5d4 It's often said that knights prefer closed positions. If we look at it from that perspective, this move makes a lot of sense, especially since it gains time by threatening the white knight. Fortunately, things in chess are more complicated than that, which is why it's so fascinating. 8. c3b1  8... f8d6  9. c2c3 A rare move. 9... c6c5 